The present invention concerns a drum press for separating liquid from solid substance, said drum press consisting of two different sized, cylindrical, perforated drums rotating one within the other around different centres, and between the envelope surfaces of which the liquid from the substance being pressed is pressed out, and said outer drum being provided with non-rotating end plates disposed with an appropriate clearance to the rotating outer drum.
In cylindrical drum presses in current use, the inner drum is frequently unperforated because it is inconvenient, expensive or outright impossible to conduct the liquid away from the inner drum, owing to the construction of such presses. A perforated inner drum in the press increases the hole surface to be nearly double in the pressing situation, and using the same pressures as in a press with unperforated inner drum, better pressing results are achieved because the liquid may pass out from the substance being pressed by a shorter route when the pressing thickness is the same, that is, of two equal-sized presses the one with perforated inner drum has about double capacity in terms of matter to be pressed, with unchanged result of the pressing operation.